From: Patrick Steinhardt <ps@pks.im>
To: Christian Couder <christian.couder@gmail.com>
Cc: git <git@vger.kernel.org>
Subject: Re: [PATCH 1/6] fetch: increase test coverage of fetches
Date: Thu, 17 Feb 2022 12:13:14 +0100 [thread overview]
Message-ID: <Yg4tyssgW9OAu6K/@ncase> (raw)
In-Reply-To: <CAP8UFD2HswmXhqYTAMxQ0iYFtsErMS=DB18iv52Ujs=cAW9ytw@mail.gmail.com>
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On Tue, Feb 15, 2022 at 07:19:19AM +0100, Christian Couder wrote:
> On Fri, Feb 11, 2022 at 8:38 PM Patrick Steinhardt <ps@pks.im> wrote:
> >
> > The `--atomic` flag is missing test coverage for pruning of deleted
> > references and backfilling of tags, and of course both aren't covered
> > correctly by this flag.
>
> It's not clear to me what "both aren't covered correctly by this flag"
> actually means here. If it means that pruning of deleted references
> and backfilling of tags don't work correctly when --atomic is used,
> then it could be stated more clearly. Otherwise this seems to just be
> repeating the first part of the sentence.
Yeah, the commit message was a bit lazy to be honest. I've reworded it
to hopefully make clearer what one is looking at.
> > Furthermore, we don't have tests demonstrating
> > error cases for backfilling tags.
> >
> > Add tests to cover those testing gaps.
> >
> > Signed-off-by: Patrick Steinhardt <ps@pks.im>
>
> > +test_expect_success 'atomic fetch with failing backfill' '
> > + git init clone3 &&
> > +
> > + # We want to test whether a failure when backfilling tags correctly
> > + # aborts the complete transaction when `--atomic` is passed: we should
> > + # neither create the branch nor should we create the tag when either
> > + # one of both fails to update correctly.
> > + #
> > + # To trigger failure we simply abort when backfilling a tag.
> > + write_script clone3/.git/hooks/reference-transaction <<-\EOF &&
> > + #!/bin/sh
> > +
> > + while read oldrev newrev reference
> > + do
> > + if test "$reference" = refs/tags/tag1
> > + then
> > + exit 1
> > + fi
> > + done
> > + EOF
> > +
> > + test_must_fail git -C clone3 fetch --atomic .. $B:refs/heads/something &&
> > +
> > + # Creation of the tag has failed, so ideally refs/heads/something
> > + # should not exist. The fact that it does is demonstrates that there is
>
> s/The fact that it does is demonstrates/The fact that it does demonstrates/
>
> > + # missing coverage in the `--atomic` flag.
>
> Maybe s/missing coverage/a bug/ would make things clearer.
>
> > + test $B = "$(git -C clone3 rev-parse --verify refs/heads/something)"
> > +'
>
> As this patch series is about fixing buggy parts of the behavior with
> --atomic, I think it would make more sense to use test_expect_failure,
> instead of test_expect_success, in this test, and to check that we
> have the correct behavior, instead of checking that we have the buggy
> behavior.
>
> Of course when later in this patch series the buggy behavior is fixed,
> then test_expect_failure should be replaced with test_expect_success.
The downside of using `test_expect_failure` is that one cannot easily
see what exactly is broken in the testcase. Yes, you can document it,
but when using `test_expect_success` the huge advantage is that you can
see exactly what behaviour is changing in subsequent commits by just having a look
at the diff of the test which adapts it from its initially-broken state
to the newly-fixed behaviour.
> > +test_expect_success 'atomic fetch with backfill should use single transaction' '
> > + git init clone4 &&
> > +
> > + # Fetching with the `--atomic` flag should update all references in a
> > + # single transaction, including backfilled tags. We thus expect to see
> > + # a single reference transaction for the created branch and tags.
> > + cat >expected <<-EOF &&
> > + prepared
> > + $ZERO_OID $B refs/heads/something
> > + $ZERO_OID $S refs/tags/tag2
> > + committed
> > + $ZERO_OID $B refs/heads/something
> > + $ZERO_OID $S refs/tags/tag2
> > + prepared
> > + $ZERO_OID $T refs/tags/tag1
> > + committed
> > + $ZERO_OID $T refs/tags/tag1
> > + EOF
>
> The comment says that we expect to see a single reference transaction,
> but the expected file we create seems to show 2 transactions. So I
> think here too, we should use test_expect_failure, instead of
> test_expect_success, and check that we have the correct behavior
> instead of a buggy one.
Same comment as above. I've also amended the commit message to say why
we're introducing the tests like this.
> > + write_script clone4/.git/hooks/reference-transaction <<-\EOF &&
>
> Here there is no #!/bin/sh while other uses of write_script in your
> patch have it. If it's not necessary, it could be removed in the other
> uses.
Good point, I always forget that the shebang is added automatically by
this helper.
> > + ( echo "$*" && cat ) >>actual
> > + EOF
> > +
> > + git -C clone4 fetch --atomic .. $B:refs/heads/something &&
> > + test_cmp expected clone4/actual
> > +'
>
> I took a quick look at the 2 other tests after this one, and I think
> test_expect_failure should be used there too, instead of
> test_expect_success.
Patrick
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next prev parent reply other threads:[~2022-02-17 11:14 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-11 7:46 [PATCH 0/6] fetch: improve atomicity of `--atomic` flag Patrick Steinhardt
2022-02-11 7:46 ` [PATCH 1/6] fetch: increase test coverage of fetches Patrick Steinhardt
2022-02-15 6:19 ` Christian Couder
2022-02-17 11:13 ` Patrick Steinhardt [this message]
2022-02-11 7:46 ` [PATCH 2/6] fetch: backfill tags before setting upstream Patrick Steinhardt
2022-02-15 6:43 ` Christian Couder
2022-02-11 7:46 ` [PATCH 3/6] fetch: control lifecycle of FETCH_HEAD in a single place Patrick Steinhardt
2022-02-15 7:32 ` Christian Couder
2022-02-17 11:18 ` Patrick Steinhardt
2022-02-11 7:46 ` [PATCH 4/6] fetch: report errors when backfilling tags fails Patrick Steinhardt
2022-02-15 7:52 ` Christian Couder
2022-02-17 11:27 ` Patrick Steinhardt
2022-02-17 12:47 ` Patrick Steinhardt
2022-02-16 23:35 ` Jonathan Tan
2022-02-17 1:31 ` Elijah Newren
2022-02-11 7:47 ` [PATCH 5/6] fetch: make `--atomic` flag cover backfilling of tags Patrick Steinhardt
2022-02-15 8:11 ` Christian Couder
2022-02-16 23:41 ` Jonathan Tan
2022-02-17 11:37 ` Patrick Steinhardt
2022-02-17 1:34 ` Elijah Newren
2022-02-17 11:58 ` Patrick Steinhardt
2022-02-11 7:47 ` [PATCH 6/6] fetch: make `--atomic` flag cover pruning of refs Patrick Steinhardt
2022-02-15 9:12 ` Christian Couder
2022-02-17 12:03 ` Patrick Steinhardt
2022-02-16 23:39 ` Jonathan Tan
2022-02-17 1:40 ` Elijah Newren
2022-02-17 12:06 ` Patrick Steinhardt
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